Malignancy-associated changes of tumor cell membrane sialoglycoproteins and sialoglycolipids (gangliosides) have been observed for decades and are implicated in many aspects of the transformed phenotype, including altered adhesive properties and metastatic potential (Bhavanandan, V. P., Furukawa, K., In: A. Rosenberg (ed.), Biology of the Sialic Acids, pp. 144–196, Plenum Press, New York (1995)). Altered, re-expressed or over-expressed sialoglycoconjugates, viewed as tumor-associated antigens (TAAs), are being investigated as targets for a variety of antibody-directed cancer therapies. Some examples include monoclonal antibodies (mabs) directed against sTn (TAG-72) in breast cancer therapy (Estava, F. J. and Hayes, D. F. Monoclonal antibody-based therapy of breast cancer. In: M. L. Grossbard (ed.), Monoclonal antibody-based therapy of cancer, pp. 309–338, Marcel Dekker, New York (1998)) and mabs to gangliosides such as GD2, GD3 and GM2 in the therapy of lung cancer and melanoma (Butler, M. O. and Haluska, F. G., In: M. L. Grossbard (ed.), Monoclonal antibody-based therapy of cancer, pp. 339–364, Marcel Dekker, New York (1998); Grant, S. C. et al., In: M. L. Grossbard (ed.), Monoclonal antibody-based therapy of cancer, pp. 365–395, Marcel Dekker, New York (1998)). Nevertheless, there remains a need for new ways to detect and treat cancer in patients.